In overhead travelling carriage systems, load ports are provided at processing devices for semiconductors or liquid crystal displays so that articles can be transferred between a platform of an overhead travelling carriage and the load ports. Of course, the load ports may be provided at positions different from those of the processing devices. Data on articles at load ports must be taught to the overhead travelling-carriage. Thus, the inventors have proposed a system in which teaching is carried out by allowing a platform of an overhead travelling carriage to grip a teaching unit comprising a touch panel and providing each load port with a mark that gets into touch with the touch panel, for teaching to the overhead travelling carriage (The Japanese Patent No. 3479969). In this case, the platform lowers from the overhead travelling carriage toward the load port and the mark gets into touch with the touch panel, and then, on the basis of the height at which the mark has touched the touch panel, the height of the load port is taught to the overhead travelling carriage. On the basis of the position at which the mark has touched the touch panel, the horizontal plane position of the load port is taught to the overhead travelling carriage.